+1 degree F per day, 2F/day max. Gentle - its easier to cause yeast stress at higher ABV.
Since gravity is still dropping, I wouldn't worry about it too much. You're bound to get another point or two, which would put you on the drier / higher ABV side of the style (and higher than most Trappist brands).
If anything, a gentle rise in temp will encourage yeast to stay in suspension and clean up fermentation by-products.
I always have difficulty maintaining ~80F temps in my ferm fridge with a heat wrap. If you can't keep the temp +/- 1 degree, its better to just hold it steady.